Host selection from attributes

Starting in ASP.NET 3, it is also possible to restrict a route based on the host header and port. You can either do that through attributes or by using fluent (code-based) configuration.

Here's an example of using attributes:

[Host("localhost", "127.0.0.1")]
public IActionResult Local() { ... }

[Host("localhost:80")]
public IActionResult LocalPort80() { ... }

[Host(":8080")]
public IActionResult Port8080() { ... }

We have three examples of using the [Host] attribute here:

1. The first one makes the Localaction method reachable only if the local header is localhost or 127.0.0.1; any number of host headers can be provided.
2. The second example demands a combination of host header and port, in this case, 80.
3. The final one just expects port 8080.

The [Host] attribute can, of course, be combined with any [Http*] or [Route] ones.

Here's how to do this through code:

endpoints.MapControllerRoute("Local", "Home/Local").RequireHost("localhost", "127.0.0.1");

This example only accepts requests from either "localhost" or "127.0.0.1" (generally these are synonyms) for the given route.

Now, the next topic will be how to specify defaults for route template parameters.